Biogas Production Using Geomembrane Plastic Digesters As Alternative Rural Energy Source and Soil Fertility Management

Sustainable Energy, 2014, Vol. 2, No. 1, 12-19 Available online at http://pubs.sciepub.com/rse/2/1/3 © Science and Education Publishing DOI:10.12691/rse-2-1-3 Biogas Production Using Geomembrane Plastic Digesters as Alternative Rural Energy Source and Soil Fertility Management Seid Yimer1, Bezabih Yimer2, Omprakash Sahu1,* 1Department of Chemical Engineering, KIOT, Wollo University, Kombolcha, Ethiopia 2Mersa Agricultural TVET College, Woldya, Ethiopia *Corresponding author: [email protected] Received December 18, 2013; Revised January 10, 2014; Accepted January 20, 2014 Abstract The aim of work is to evaluate amount of gas production, economical feasibility and quality of slurry for geomembrane plastic biogas plants constructed below and above the ground surface and fixed-dome biogas plant of 3 m3 capacity. Amount of gas and slurry were measured using calibrated biogas burner and weight balance respectively. The qualities of the slurry were analyzed in the laboratory using Kjeldahl and ash method respectively. Economic evaluation and comparison of the biodigester was carried out using cost-benefit analysis. Gas production and total-N was higher for a single layered and above ground plastic biodigester than others. Fermented slurry contained larger nitrogen content than fresh cow dung in both models of biodigester. The geomembrane plastic biogas plant gave higher net benefit than fixed-dome biogas plant. The biogas technology was found to increase income generation through increased crop production with the use of nutritive slurry as organic fertilizer and solve the problem of fuel shortage in the rural areas. Environmental impact assessment of the technology was studied and 3 3 found that from the use of a geomembrane plastic biodigester, 360 m of CO2 and 600 m CH4 was prevented from emitting in to the atmosphere and save 0.562 hectare of forest per year from being deforested and hence attributed towards the decrease in global warming. Generally, the geomembrane cylindrical film biodigester technology was found cheap and simple way to produce gas in the study area. Keywords: economical, feasibility, geomembrane, slurry Cite This Article: Seid Yimer, Bezabih Yimer, and Omprakash Sahu, “Biogas Production Using Geomembrane Plastic Digesters as Alternative Rural Energy Source and Soil Fertility Management.” Sustainable Energy, vol. 2, no. 1 (2014): 12-19. doi: 10.12691/rse-2-1-3. fuels has caused serious air pollution problems, likewise the excessive consumption of fire wood results in 1. Introduction deforestation on a large scale. IUCN (1990) [5] estimated that high forests covered 16% of the land area of Ethiopia The continuous depletion of fossil fuel is sticking the in the early 1950 s, 3.6% in the early 1980 s and 2.7% in concern into the search for new energy sources to be used. 1989. Biogas digestion was introduced into developing The potential energy sources have been emerged as countries as a low-cost alternative source of energy to renewable energy resources. For a long time multifarious partially alleviate the problem of acute energy shortage for sources of renewable energy are being investigated to households, reduces deforestation and soil erosion, avoids meet the increasing energy consumption rate. To scarcity of firewood, benefits environment globally and counteract with the growing demand researchers are provides excellent fertilizer [6]. exploring the new sources. The developing countries are Biogas plants are a closed container in which anaerobic going ahead to face the shortage of available energy. fermentation of cellulose containing organic material takes Dependency from biomass such as fuel wood, charcoal, place so as to produce biogas and slurry. There are three dried cow dung cake and crop residue in Ethiopia amounts basic designs of biogas plant popular in the world. These to 95% (Benjamin, 2004). According to MOA (2000), on are the floating-drum type, fixed-dome type and bag average each rural household spends ten hours per week digester. The floating-drum and fixed-dome type biogas searching for fuel wood. Females & children are engaged plants have been introduced to Ethiopia. However, they to search fire wood for about 5-6 hours journey [1]. When became an obstacle to the rapid diffusion of biogas all forest uses are included, the deforestation rate in technology, because it takes a relatively long time (3-5 Ethiopia is around 1.1% per year [2]. According to Bech week) to build a plant, high initial cost of investment, et al. [3], the forest cover of North Wollo and Habru shortage of adequate skilled person who can undertake district is 37,183.58 hectare and 1614 hectare respectively. construction & installation of the plant and transportation According to FAO (2000) [4], the combustion of fossil problem of the prefabricated steel drum from the urban Sustainable Energy 13 areas to the interior rural regions of Ethiopia [7]. The Number of cattle required was calculated by using the introduction of the geomembrane plastic bag digester have formula, not yet been experimented in Ethiopia. Considering the Totaldung problem of biogas technology dissemination with the (2) existing biogas plants, the study was conducted on Dung/ animal alternative biogas plants constructed using geomembrane The volume of the digester was calculated as plastic in cylindrical shape. In this regard’s an effort has been made to introduce geomembrane plastic biogas plant, Quantity of daily dung required / digester comparisons of gas and slurry yield and economic Weightof() dung+ water (3) feasibility analysis with the fixed-dome biodigester should = Densityofslurry be done and accordingly, the outcome of the study may have some contribution to set remedy to the problem. Minimum digester volume (DO) = Volume of daily charge * Retention time Actual digester volume = DO + 0.1 DO. 2. Materials and Methods The volume of gas holder was calculated as, 2.1. Description of the Study Area V= ( volume of gas production) (4) The experiment was conducted in Mersa Agricultural Total volume for geomembrane biodigester = Volume T.V.E.T College, Ethiopia at 11°35’N latitude and of digester + Volume of gas holder. 39°38’E longitude with an altitude of 1557 m above sea Hydrostatic pressure due to the slurry acting on the level. The area is classified under moist warm climatic inner surface which exerts tensile load on the digester wall zone with mean annual rainfall of 1090 mm and with an was calculated as = depth of slurry * density of slurry. average daily temperature of 21.12°C. According to Santra [9], a ratio of 4 in length to one in diameter was used to produce much gas and quality 2.2. Geomembrane Plastic Biodigester Design fertilizer in horizontal biogas plants. Where D = diameter Parameters and L= length and accordingly the dimension of the cylindrical plastic biodigester was calculated as A. Selection of materials. = Construction materials: geomembrane plastic 0.5 mm in V DL2 /4 (5) thickness, PVC pipes. Input materials are cow dung and water. 2.3. Experimental Design and Layout B. Temperature: Mesophilic (21.4°C). Four biodigester were made from single & double C. Mixing ratio of substrate 1:1. I.e. 75 kg of cattle layered cylindrical geomembrane plastic film, constructed dung was mixed with 75 liters of water. Total dung below the ground on a trench excavated at a dimension of required per day was calculated as [8]. 7 m * 1.5 m * 0.5 m and above the ground surface on a Total dung required / day concrete block wall platform constructed at a dimension of 7 m*1.5 m*(0.75 m and 0.5 m) with a slope of 2°. One Gasproduction/ day (1) = Chinese model fixed-dome biogas plant was also another Gas/ Kgofreshdung treatment. The capacities of the digesters were 3 m3. The D. Hydraulic Retention Time (HRT). experiment duration was from Nov. 2011 to July 2012. For mesophilic temperature of Mersa locality, HRT is The treatments of the experiment were: selected as 40 days. Figure 1. Layout of the Experimental Site 14 Sustainable Energy PSA: plastic biodigester, single layered and during the study. Amount of gas production, quantity of constructed above ground. input and output slurry, temperature of the air, pH of the PDA: plastic biodigester double layered and fresh cow dung and digested slurry, total–N and organic constructed above ground. matter content of the substrate and the slurry. Daily PSU plastic biodigester single layered and rainfall, temperature of the air and slurry was also constructed under ground. measured. PDA plastic biodigester double layered and constructed underground. 2.5.1. Input to the Digesters FDU: Fixed dome biodigester constructed The type of input material which was found feasible underground. and available in the study area was cow dung as there was The manure was collected from Mersa Agricultural dairy farm at a distance of 25 meter from the experiential TVET College dairy farm and the nearby private cattle site. Manure inputs were measured using bucket of 25 liter. shed. One bucket of cattle dung was mixed with 1 bucket of water [8]. Thus, as per the design three bucket of dung (75 2.4. Geomembrane Plastic Construction Kg) were mixed with three bucket of pure water (75 litres) Methodology so as to produce 3 m3 gas per day on May 5, 2007. After the slurry mixture has been fed in to the digester, 15 liters Materials used for the construction of geomembrane starter material prepared from cattle dung and water in 1:1 plastic biodigester were geomembrane plastic, PVC pipes, ratio and allowed to ferment for one month in a closed gate valves, GI caps, sockets, nipples, neoprene rubber barrel were added at equal amount to all five biodigester hose and biogas stoves. Construction was done with the to initiate and facilitate the fermentation process. help of electrical geomembrane welding machine and CM-43 adhesive with other mixtures.

Load more